Patent GB-627824-A (GB)
Title: Improvements in sighting arrangements for guns and the like
IPC: F41G5/00
Filed: 1944-01-31
Abstract: 627,824. Sighting-apparatus. TUSTIN, A., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Jan. 31, 1944, No. 1813. [Class 92 (ii)] [Also in Group XXXVIII] In a sighting- apparatus for guns means is provided to displace the sight with respect to the gun about two axes, the device comprising a magnetic armature 1 mounted for movement about two mutually perpendicular axes 5, 6, and 7, 8, and provided with partspherical surface elements generated about the centre of intersection of the two axes. The armature is combined with a magnet system comprising two annular yokes 10, 11, the yoke 10 carrying four poles E1, E2, T1, T2, and the yoke 11 carrying four corresponding poles of which T1<SP>1</SP>, T2<SP>1</SP>, appear in Fig. 2. The pole faces are of part spherical form about the same centre as the armature and are disposed radially about the centre and arranged perpendicularly to one another, the pole pieces having excitation windings e, e<SP>1</SP> adapted to produce magnetic forces tending to tilt the armature in dependence of the desired displacements of the sight with respect to the training and elevating axes. In the construction shown, the armature is carried by a gimbal system from a pillar 3 secured to the gun, the system comprising a ring 4 connected by the pivots on the axes 5 ... 8 to the pillar and armature, as shown. Springs 13, 14, around the pivots, tend to restore the ring and armature to a central position and the armature is fitted at one end with a mirror 9 arranged in the optical system of the sight. The eight pole-pieces are carried four on each of the two yokes 10, 11 magnetically connected at their periphery by a flange 12 on yoke 10 as shown in Fig. 2. As applied in Fig. 3 to a sight wherein the prediction correction is obtained by multiplying the range or time of flight by the angular velocity of the gun in training and elevation, a resistor 17 in circuit with the eight coils e, all arranged in series, is adjusted until a dial of an ammeter 18 gives a reading corresponding to the range or time of flight. The drawing gives the azimuth circuit only, and, as shown, the coils e are so wound as to induce opposite polarity on diametrically opposite poles T<SP>1</SP> and T<SP>2</SP> on the one hand and T1<SP>1</SP> and T2<SP>1</SP> on the other hand, but similar polarity in the two poles of each aligned pair. These four poles are provided with the further coils e<SP>1</SP> which are in circuit with a tachometer generator 19 connected to the gun so as to produce a voltage dependent on the angular velocity of the gun in azimuth. The coils are so wound that they act in the opposite direction to one another on poles T<SP>1</SP> and T<SP>2</SP>, and also on T1<SP>1</SP> and T2<SP>1</SP>, and oppositely to one another on aligned poles T<SP>1</SP>, T1<SP>1</SP> and T<SP>2</SP>, T2<SP>1</SP>. The resultant forces which act tangentially on the armature produce a torque thereon which is dependent on the difference between the square of the sum and the square of the difference between the two components of excitation, the torque thereby being proportional to the product of these components to give the required prediction correction to the sight. Specification 617,591, [Group XXXVIII], is referred to.